First Luger, help needed

[Doubs]

The 1920 is neat enough to be a date stamp and the inspection/proof marks are those used in that time period. The 1920 property stamps were applied at unit level by armorers and are usually not that neatly done.

This is just my opinion. From the Nazi era eagle stamps, I think it was re-proved in the mid-1930's for some reason. It could be for a barrel replacement as Norm says.